Geology topics

J.C. Shaw

Publications and source records attributed to J.C. Shaw.

3 recordsLinked to original sources

USGS2012

Digenean metacercariae of ﬁshes from the lagoon ﬂats of Palmyra Atoll, Eastern Indo-Paciﬁc

Although many studies on the taxonomy of digenean trematodes of marine fishes have been completed in the Eastern Indo-Pacific (EIP) marine ecoregion, only a few have considered metacercarial stages. Here, the results are presented of a taxonomic survey of the digenean metacercariae of fishes from Palmyra Atoll, a remote and relatively pristine US National Wildlife Refuge located 1680 km SSW of Hawaii. Up to 425 individual fish were collected, comprising 42 fish species, from the sand flats bordering the lagoon of the atoll. Quantitative parasitological examinations of each fish were performed. Morphological descriptions of the encountered digenean metacercariae are provided, together with their prevalence, mean intensities, host and tissue-use. Up to 33,964 individuals were recovered representing 19 digenean metacercaria species from eight families. The species composition of digeneans in lagoon fishes at Palmyra Atoll is a subset of what has previously been reported for the EIP. Further, the large diversity and abundance of metacercariae reported in this study highlight the utility of including this group in future ecological research in the EIP marine ecoregion.

Journal of Helminthology↗

USGS2010

Ecology of the brain trematode Euhaplorchis californiensis and its host, the California Killifish (Fundulus parvipinnis)

We describe the distribution and abundance of the brain-encysting trematode Euhaplorchis californiensis and its second intermediate host, the California killifish ( Fundulus parvipinnis ), in 3 estuaries in southern California and Baja California. We quantified the density of fish and metacercariae at 13–14 sites per estuary and dissected 375 killifish. Density (numbers and biomass) was examined at 3 spatial scales, i.e., small replicate sites, habitats, and entire estuaries. At those same scales, factors that might influence metacercaria prevalence, abundance, and aggregation in host individuals and populations were also examined. Metacercaria prevalence was 94–100% among the estuaries. Most fish were infected with 100s to 1,000s of E. californiensis metacercariae, with mean abundance generally increasing with host size. Although body condition of fish did not vary among sites or estuaries, the abundance of metacercariae varied significantly among sites, habitats, estuaries, and substantially with host size and gender. Metacercariae were modestly aggregated in killifish ( k > 1), with aggregation decreasing in larger hosts. Across the 3 estuaries, the total populations of killifish ranged from 9,000–12,000 individuals/ha and from 7–43 kg/ha. The component populations of E. californiensis metacercariae ranged from 78–200 million individuals/ha and from 0.1–0.3 kg/ha. Biomass of E. californiensis metacercariae constituted 0.5–1.7% of the killifish biomass in the estuaries. Our findings, in conjunction with previously documented effects of E. californiensis , suggest a strong influence of this parasite on the size, distribution, biomass, and abundance of its killifish host.

Journal of Parasitology↗

USGS2008

Parasite manipulation of brain monoamines in California killifish (Fundulus parvipinnis) by the trematode Euhaplorchis californiensis

California killifish (Fundulus parvipinnis) infected with the brain-encysting trematode Euhaplorchis californiensis display conspicuous swimming behaviours rendering them more susceptible to predation by avian final hosts. Heavily infected killifish grow and reproduce normally, despite having thousands of cysts inside their braincases. This suggests that E. californiensis affects only specific locomotory behaviours. We hypothesised that changes in the serotonin and dopamine metabolism, essential for controlling locomotion and arousal may underlie this behaviour modification. We employed micropunch dissection and HPLC to analyse monoamine and monoamine metabolite concentrations in the brain regions of uninfected and experimentally infected fish. The parasites exerted density-dependent changes in monoaminergic activity distinct from those exhibited by fish subjected to stress. Specifically, E. californiensis inhibited a normally occurring, stress-induced elevation of serotonergic metabolism in the raphae nuclei. This effect was particularly evident in the experimentally infected fish, whose low-density infections were concentrated on the brainstem. Furthermore, high E. californiensis density was associated with increased dopaminergic activity in the hypothalamus and decreased serotonergic activity in the hippocampus. In conclusion, the altered monoaminergic metabolism may explain behavioural differences leading to increased predation of the infected killifish by their final host predators. ?? 2008 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗